Valproic Acid test

Valproic acid test is a very important anti-epileptic drug why because this valproic acid has a broad spectrum anti-epileptic activity. Valproic acid is an anticonvulsant used primarily to treat epilepsy, and bipolar disorders, and to prevent migraine headaches.

Monitoring its levels in the blood helps ensure effective treatment while minimizing the risk of side effects. It is primarily a broad-spectrum antiepileptic drug.

Purpose of Valproic Acid test:

Therapeutic Monitoring:

To ensure that the drug levels are within the therapeutic range for effective seizure control and many other conditions.

Adjusting Dosage:

This will help adjust the dosage based on blood levels, especially if there are changes in the patient’s condition or response to treatment.

Evaluating Toxicity:

To identify and manage potential toxicity or adverse effects if symptoms suggest high levels.

Assessing Non-Compliance:

To verify if the patient is taking the medication as prescribed.

Therapeutic Uses:

• Myoclonic seizure (drug of choice)
• Absence seizure
• Tonic-clonic (grand mal) seizures (alternate drug)
• Bipolar disorder
• Trigeminal neuralgia
• Lennox Gas taut syndrome
• Migraine prophylaxis
• Tardive Dyskinesia

Normal Range of Valproic Acid:

Total Valproic Acid

• 50-100 picogram

Sample Collection for Valproic Acid:

• Blood samples are usually collected just before the next dose trough level to accurately reflect the lowest concentration of the drug.
• Ideally, the patient should not have taken the medication shortly before blood collection to avoid skewing results.
• Use a serum separator tube or a plain red-top tube for serum collection

Collection of High Valproic Acid in Blood:

1. Taking more than the prescribed dose
2. Certain drugs can increase valproic acid levels (e.g. certain antibiotics, and other anticonvulsants like lamotrigine).
3. Impaired liver function can affect drug metabolism, leading to higher levels.
4. Conditions like hypoalbuminemia (low albumin levels) can increase the free fraction of valproic acid.

Causes of Low Valproic Acid:

1. Taking less than the prescribed
2. Certain drugs can decrease valproic acid levels(e.g. carbamazepine, phenytoin).
3. Conditions or medications that increase drug metabolism or clearance.
4. The issue with gastrointestinal absorption.

Absorption and Fate:

• It is administered orally and is rapidly absorbed. About 90% of the drug is bound to plasma proteins. Most of the drug is metabolized in the liver 97% and only 3% is excreted unchanged.
• Valproic acid is metabolized by the cytochrome p450 system. The glucuronidated metabolites are excreted in the urine.
• The plasma half-life of valproic acid is 12-15 hours
• Valproic acid should not be stopped suddenly
• It is contraindicated in children <2 years, liver failure, and pregnancy

Adverse Effects:

• Nausea
• vomiting
• Tremor
• Drowsiness
• Hepatic failure
• Sedation
• Ataxia, Rash and alopecia
• Increase bleeding time
• Hepatotoxicity and pancreatitis

Drug Interactions:

Valproic acid inhibits its metabolism and the metabolism of other drugs, including phenobarbital, carbamazepine, phenytoin ethosuximide, and aspirin.